LAURA HURTADO NAVARRO¹, Laura Martinez Alarcon¹, Graciela Valero Navarro², Carlos Garcia Palenciano¹, PABLO PELEGRIN VIVANCOS¹

(1) CIRUGÍA DIGESTIVA, ENDOCRINA Y TRASPLANTE DE ÓRGANOS ABDOMINALES, IMIB-Arrixaca, España
(2) INVESTIGACIÓN QUIRÚRGICA EN ÁREA DE SALUD, IMIB-Arrixaca, España

Sepsis is the leading cause of death in critical care units and it is defined by a systemic inflammatory response which is followed with an immunosuppression of the host. Exacerbation of any of these two responses compromises the life of septic patients. While the function of the NLRP3 inflammasome is involved in sepsis, the function of other inflammasomes, like Pyrin inflammasome, is not well known.

Individuals with intra-abdominal origin sepsis (n=20), abdominal surgery individuals that had not developed sepsis (n=19), and a healthy control group (n=29) were recruited. NLRP3 inflammasome was stimulated in whole blood by LPS+ATP and Pyrin inflammasome with LPS+TcdB. Flow cytometry was used to determine the formation of ASC specks formation in monocytes (CD14+ CD16+ CD15-) and ELISA to determine cytokine secretion. The evolution of clinical parameters, haematological features and plasma biochemistry parameters were evaluated.

Systemic inflammatory markers like CRP or PCT were elevated in septic patients’ plasma 24h after sepsis initiation when compared to a control group of abdominal surgery patients and standardized thresholds, indicating an inflammatory state of the septic pa-tients. The release of IL-1β in whole blood samples and the formation of ASC specks in monocytes after NLRP3 stimulation resulted in a differential response among septic patients, identifying a group of 10 individuals with an impaired NLRP3 inflammasome activation, 4 individuals with sepsis presented a normal response of the NLRP3 inflammasome. However, all septic patients presented a non-impaired activation of the Pyrin inflammasome. Septic patients with impaired NLRP3 inflammasome also had biochemical and clinical scores of disease severity above the average of septic patients without impaired inflam-masome activation. SOFA and APACHEII were higher at admission in the group with NLRP3 inflammasome impairment, and these individuals also present worst disease progression measured as days in the critical care unit, days with mechanical ventilation and mortality. Plasma concentration of CRP and PCT decreased after 3 and 5 days of sepsis onset in all septic patients, indicating a gradual resolution of systemic inflammation. At hospital discharge, NLRP3-immunocompromised septic patients who survived and recovered from sepsis had an improvement on NLRP3 activation. Non-compromised NLRP3 septic patients had normal ASC-speck formation during the course of sepsis. This suggests that NLRP3 inflammasome impairment during sepsis is a transitory state. Our study confirms the previously results obtained from a discovery cohort, in which during the initial inflammatory response in sepsis there is a differential response of the NLRP3 inflammasome in septic patients. The identification of NLRP3-immunocompromised septic patients was optimized in a whole blood assay and accounted for most late deaths and have the worse prognosis. Whereas, the Pyrin inflammasome response was similar in patients and suggests that Pyrin inflammasome present different regulation mechanisms inflammasome during sepsis.

The impairment of the NLRP3 inflammasome in septic patients might serve as an early indication of immunosuppression in critical patients, while the Pyrin inflammasome emerge as a positive control of inflammasome activation. Moreover, restoration of NLRP3 inflam-masome activation in monocytes could be a good indicator of immune recovery in septic patients.